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      <title>分布式锁中 线程获取到锁了此时redis宕机了怎么办 - 交互式测验</title>
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            <div class="quiz-header">
              <h1>分布式锁中 线程获取到锁了此时redis宕机了怎么办 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
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      <script>
        const quizData = [
  {
    "question": "根据文档，当使用Redis实现分布式锁时，设置“自动过期时间”主要解决了什么问题？",
    "options": [
      "提高获取锁的性能和吞吐量。",
      "避免因服务宕机或客户端异常导致锁被无限期占用，从而造成死锁。",
      "实现锁的可重入性，允许同一线程多次获取锁。",
      "保证在Redis宕机后，锁能够立即被其他线程获取。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "设置锁的过期时间是一种核心的容错机制。它确保即使持有锁的客户端崩溃或者Redis服务宕机后未能正常释放锁，该锁也会在预设的时间后自动被Redis删除，从而避免了锁被永久占用的情况，防止系统发生死锁。",
    "source": "文档中「使用锁的自动过期时间」部分",
    "hint": "思考一下，如果一个线程拿了锁之后就崩溃了，没有机会释放锁，会发生什么？这个机制就是为了防止最坏情况的发生。"
  },
  {
    "question": "文档中提到的“使用备用锁机制”是一种怎样的容错策略？",
    "options": [
      "当主锁服务（如Redis）不可用时，系统自动切换到另一种锁实现（如基于ZooKeeper或数据库）。",
      "定期将Redis的锁数据备份到磁盘，以便宕机后快速恢复。",
      "在同一个Redis实例中为重要的锁创建多个副本作为备份。",
      "为每个锁设置一个备用值，在主值失效时启用。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "备用锁机制是一种高可用设计思想。它意味着系统不依赖单一的锁服务。当首选的锁服务（Redis）发生故障时，系统能够智能地、自动地切换到预先准备好的第二套锁方案上，例如使用ZooKeeper或数据库实现的分布式锁，从而保证核心业务的连续性。",
    "source": "文档中「使用备用锁机制」部分",
    "hint": "这个策略的核心思想是“Plan B”。当你的第一选择失效时，系统应该怎么做？"
  },
  {
    "question": "为什么文档推荐使用像Redisson或Curator这样的成熟分布式锁框架？",
    "options": [
      "因为这些框架可以完全避免Redis或ZooKeeper的宕机。",
      "因为它们是唯一能够实现分布式锁的方式。",
      "因为这些框架提供了更健壮和稳定的实现，能够妥善处理像服务宕机这样的复杂异常情况。",
      "因为这些框架的性能通常比手动实现的锁要低，但更安全。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "自己从零开始实现一个健壮的分布式锁非常复杂，需要处理很多边界情况，比如锁的自动续期（Watchdog机制）、公平锁、可重入性以及节点故障等。成熟的框架（如Redisson）已经封装好了这些复杂逻辑，提供了经过大规模生产环境验证的、稳定可靠的解决方案。",
    "source": "文档中「使用分布式锁框架」部分",
    "hint": "文档中提到，这些框架“提供了更加稳定和健壮的分布式锁实现”。"
  },
  {
    "question": "文档中“采用心跳检测机制”的核心作用是什么？",
    "options": [
      "为已经获取的锁进行“续期”，防止锁在业务未完成时过期。",
      "主动监控Redis的健康状态，以便在发现宕机时能迅速通知业务模块并启动容错策略。",
      "检测客户端与Redis之间的网络延迟，并自动优化路由。",
      "在Redis宕机时，自动重启Redis服务进程。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "心跳检测是一种主动的健康检查方式。客户端或一个独立的监控服务会定期向Redis发送“心跳”请求，并期望得到正常的响应。如果连续多次未收到响应，就可以判断Redis服务可能已宕机，从而可以立即触发报警或执行预设的容错预案，如服务降级或切换到备用锁机制。",
    "source": "文档中「采用心跳检测机制」部分",
    "hint": "这个机制的功能类似于医生为病人测量脉搏，目的是为了及时发现“生命体征”是否正常。"
  },
  {
    "question": "在文档「实现锁的重入机制」一节中，描述了当线程获取锁后发现Redis宕机时，应该采取什么行动？",
    "options": [
      "立即向监控系统报告错误并终止当前操作。",
      "允许同一个线程在未释放锁的情况下再次获得该锁。",
      "尝试重新获取锁或等待一段时间后再次尝试。",
      "立即切换到基于数据库的备用锁机制。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "该章节描述了一种应对策略。当持有锁的线程在执行业务逻辑时（例如，在释放锁之前），发现Redis连接断开或宕机，它不应立即放弃。文档建议可以实现一种重试逻辑，即等待一小段时间后，再次尝试连接并操作锁，看服务是否已经恢复。",
    "source": "文档中「实现锁的重入机制」部分",
    "hint": "注意题目问的是该章节的“描述”。请仔细阅读原文：“如果线程获取锁后发现Redis宕机，可以尝试重新获取锁或等待一段时间后再次尝试”。"
  },
  {
    "question": "综合全文，实施自动过期、健康监控、备用机制等多种策略的最终目的是什么？",
    "options": [
      "保障系统在面对Redis宕机等故障时的稳定性和可靠性。",
      "最大限度地提升分布式锁的执行效率和性能。",
      "简化分布式系统的整体架构和开发复杂度。",
      "实现跨数据中心的强一致性事务。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "文档中提到的所有措施，无论是预防性的（如设置过期时间）、检测性的（如监控和心跳）还是恢复性的（如备用机制、重试），都是为了一个共同的目标：增强系统的容错能力。这样，当像Redis宕机这样的单点故障发生时，整个系统不会因此崩溃，而是能够优雅地处理异常，保持服务的稳定和可靠。",
    "source": "文档结尾总结部分",
    "hint": "文档在最后一段明确指出，通过这些机制可以“有效应对Redis宕机对系统造成的影响，保障系统的稳定性和可靠性”。"
  }
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            const wrongCount = answeredCount - correctCount;
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                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  